Method for recovering metallic materials of gas generator for air bag

ABSTRACT

To provide a method for taking out gas generators readily from waste vehicles and then recovering metallic materials of gas generators taken out efficiently. The method is comprised by a) crushing waste vehicles in which air bag apparatuses are installed by a crushing means so that the crushed pieces have approximately the same size as that of the gas generators themselves and the gas generators themselves can be separated from the air bag apparatuses as single bodies without being substantially crushed; b) taking the gas generators out of the crushed pieces of the waste vehicles; c) charging the gas generators thus taken out into a melting furnace; and d) recovering the metallic materials of the gas generator from the melting furnace.

FIELD OF THE INVENTION

The present invention relates to a method for disposing of a gasgenerator for an air bag which is used for protecting a passenger fromimpact, specifically to a method for taking out a gas generator from awaste vehicle and recovering metallic materials from the gas generator.

DESCRIPTION OF PRIOR ART

An air bag apparatus(es) is installed in a vehicle for the purpose ofprotecting passengers from impact caused by collision. This air bagapparatus comprises an air bag to be expanded by gas at collision toform a cushion between a passenger and a steering wheel or seat, and agas generator to feed gas into the air bag.

A gas generator is comprised of a housing made of a metallic material, agas generating agent disposed in this housing and an ignition means forigniting this gas generating agent. The ignition means is actuated byimpact, and this causes the gas generating agent to burn to generatehigh temperature and high pressure gas.

A member for forming the housing of the gas generator is made of, forexample, aluminum or stainless steel. The gas generating agent includes,for example, NaN₃ (sodium azide), CuO (copper monoxide) and the like asa principal component. In addition to the above, parts such as a filtercomprising a stainless metal mesh, stainless wool and ceramic, etc., anda coolant are contained in the gas generator.

In order to take out a gas generator from an air bag apparatus installedin a waste vehicle, the following manual procedure is used: detaching anair bag apparatus from a steering wheel; disassembling the detached airbag apparatus in order, beginning with an air bag cover, an air bag, agas generator and a steering wheel adaptor; and then, recovering the gasgenerator.

A method disclosed in, for example, U.S. Pat. No. 5,294,244 is availableas a method for recovering metallic materials from a gas generator. Inthis method, metallic materials are recovered separately by making useof a difference in the melting points of the metallic materials.According to this method, a gas generator containing aluminum alloyparts and non-aluminum alloy parts are heated in the range of themelting point of aluminum to recover aluminum alloy, and then theremaining non-aluminum alloy parts are heated up to a higher temperaturethan the melting point of stainless steel alloy to recover stainlesssteel alloy.

As a method for recovering metallic materials from a gas generator, thegas generator is crushed or pulverized, and the metallic materials ofthe gas generator are classified from the pulverized solid particles bymagnetic separation or gravity separation etc. to melt the separatedmaterials into ingots.

In the preceding conventional method for recovering a gas generator bymanual operation, there are problems that the recovering efficiency isvery low and the recovering cost becomes expensive as well because ofthe fact that first of all, a waste vehicle in which an air bagapparatus(es) is installed has to be found out among waste vehicles nothaving an air bag apparatus(es), and that labor and time are required asdescribed above in order to recover the gas generator from the wastevehicle found.

It is expected that the number of air bag apparatus-mounted vehicleswill increase in the future. Therefore, a method for recovering a gasgenerator from a waste vehicle at a high efficiency and low cost isdesired.

U.S. Pat. No. 5,294,244 does not refer to a method for recovering a gasgenerator from a waste vehicle.

In a conventional method in which a gas generator is crushed orpulverized in order to recover metallic materials from the gasgenerator, the housing is not easily crushed or pulverized because thehousing of the gas generator is firmly constituted and has a highrigidity. That has produced the problems that a specific blade and alarge power are required.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to solve thepreceding problems in conventional techniques.

The present invention relates to a method for recovering metallicmaterials, that is, a method for recovering metallic materials of gasgenerators for air bags from waste vehicles comprising:

a) crushing waste vehicles in which air bag apparatuses are installed bya crushing means adjusted so that the crushed pieces have approximatelythe same size as that of the gas generators themselves, and the gasgenerators themselves without being substantially crushed can beseparated in the form of a single body from the air bag apparatuses,

b) taking the gas generators out of the crushed pieces of the wastevehicles,

c) charging the gas generators thus taken out into a melting furnace,and

d) recovering the metallic materials of the gas generators from themelting furnace.

In other words, the method of the present invention is a method forrecovering metallic materials of gas generators for air bags from wastevehicles, comprising a) crushing waste vehicles in which air bagapparatus are installed by a crushing means so that the crushed pieceshave approximately the same size as that of the gas generatorsthemselves, and the gas generators themselves can be separated from theair bag apparatuses as single bodies without being substantiallycrushed; b) taking the gas generators out of the crushed pieces of thewaste vehicles; c) charging the gas generators thus taken out into amelting furnace; and d) recovering the metallic materials from themelting furnace. That is, the method of the present invention comprisescrushing waste vehicles so that the crushed pieces have approximatelythe same size as that of the gas generators themselves and the gasgenerators themselves are not substantially crushed. And the gasgenerators are taken out thereof and melted in a melting furnace torecover the metallic materials of the gas generators.

The crushing means is preferably a crusher in which vehicles are crushedby rotation of blades.

The gas generators can be taken out by classifying them into ones havinghousing made of aluminum and ones having housing made of stainlesssteel.

Further, the gas generators classified into ones having housing made ofaluminum and ones having housing made of stainless steel are preferablycharged into respective melting furnaces.

The gas generators may be actuated as well before charging them into afurnace.

In addition, the gas generators may be actuated by heating.

The present inventors have crushed a waste vehicle in which an air bagapparatus is not installed, and which has been compressed by softpressing, using a crusher (shredder manufactured by Tissenhenschel Co.,Ltd., Germany) which is used in disposing of waste vehicles withshredder rotary blades, manufactured by the same company. And thepresent inventors have observed that an average size of crushed piecesdischarged from the crusher on a belt conveyor is approximately the sameas that of a gas generator. It has been expected, therefore, that incrushing waste vehicles in which air bag apparatuses are installed, thegas generators themselves will not be crushed and will be able to beseparated from the other parts of the air bag apparatus due to thefirmness of the gas generators, since an average size of the crushedpieces is approximately the same as that of the gas generators.

In the case where the crushed pieces of waste vehicles are markedlysmaller than the gas generators, the gas generators are finely broken bycrushing, and it is difficult to distinguish the finely broken gasgenerators and take them out of the crushed pieces of the crashedvehicles.

On the other hand, in the case where the crushed pieces of wastevehicles are notably larger than the gas generators, the gas generatorsremain as part of the air bag apparatus and are mounted thereon, andtherefore this part would have to be detached from the gas generatorsthemselves by manual work.

A waste vehicle with an air bag apparatus(es) compressed by soft presshas been charged into the above mentioned crusher and was crushed. Ithas been found, as expected, that the gas generator has been separatedin the form of a single body from the air bag apparatus in the crushedpieces discharged from the crusher. It has been confirmed by the presentinventors that a gas generator can independently be taken out of a wastevehicle by crushing it with a crusher which is controlled so as to crushthe waste vehicle into pieces having such size as described above.

Further, it has been found that a gas generator having a housing made ofaluminum can readily be distinguished from a gas generator having ahousing made of stainless steel and both can be taken out separately.

If gas generators themselves have been finely broken, a chance to takeout the gas generators already having a relatively high grade has beenlost. That is, the crushed pieces have to be sent to a certainconventional metal classifying after the step of finely breaking, andpassed through such extra steps as magnetic separation, gravityseparation etc.

When taking gas generators out of waste vehicles, they are taken outpreferably classifying into the gas generators having housing made ofaluminum and the gas generators having housing made of stainless steel.This saves labor for classification when charging them into thefollowing exclusive melting furnaces, that is, a melting furnace foraluminum and a melting furnace for stainless steel and therefore makesit possible to carry out the operation efficiently.

Respective ingots can be separately obtained by charging gas generatorsinto melting furnaces classified into the gas generators having housingmade of aluminum and the gas generators having housing made of stainlesssteel and causing molten aluminum metal and molten stainless steel metalto flow into respective ingot molds.

The gas generators having housing made of aluminum and the gasgenerators having housing made of stainless steel can be charged as wellinto a melting furnace together. In this case, an aluminum ingot and astainless steel ingot can finally be obtained by making use of adifference between the melting points thereof.

When charging non-actuated gas generators into a melting furnace, thereis a risk that the gas generators are actuated in the furnace in acertain case, so that molten metal is scattered, and therefore a closedtype melting furnace is preferably used. In the case of gas generatorswhich have already been actuated, the furnace to be used does not haveto be restricted to closed type melting furnaces, and open type meltingfurnaces can be used as well.

Before non-actuated gas generators are charged into a melting furnace,they can be actuated. In this case, the gas generators can be actuatedby heating. For example, a non-actuated gas generators are heated to150° to 450° C. to ignite and completely burn the gas generating agent,whereby a safety treatment can be carried out, and the treated gasgenerators can be sent to the next step. A heating furnace can beapplied as a heating facility, and a batch system or a continuousprocessing system are available as a heating system. In the heatingfurnace of the batch system, plural nonactuated gas generators areactuated at the same time to generate a large amount of gas at once, andtherefore a safety countermeasure has to be considered.

On the other hand, in the heating furnace of the continuous processingsystem, gas generators can be actuated in succession by sending the gasgenerators into the furnace by using a transporting means such as aconveyor, and therefore such heating furnace is preferred in terms ofsafety. Further, heating time and heating temperatures for the gasgenerators can be controlled by regulating a feeding rate of the gasgenerators.

There is a fear of that gas blows out by the actuation of a gasgenerator and the gas generator flies and rushes by with an impellentforce. Accordingly, a gas generator is preferably fixed by means of afixing means. For example, a metal mesh for receiving a gas generatorand supporting bars for holding a gas generator can be used as thefixing means.

It is considered that pressure in a furnace is suddenly changed whilethe gas is generated. In order to cope with this, it is preferred that abuffer space is provided to the inner of the furnace. In order to heatnon-actuated gas generators, exhaust heat or remaining heat of a meltingfurnace into which gas generators are charged can be utilized as well.

The following methods can be used in order to actuate gas generators.

1. In the case of an electric type gas generator, it can be actuated byconnecting wire of an ignition device of the gas generator to a batteryand applying a prescribed current.

2. In the case of a mechanical type gas generator, it can be actuated byfalling into a used tire(s).

The present invention is constituted as explained above, and therefore agas generator(s) can be readily taken out of a waste vehicle. Thepresent invention can remove work for detaching gas generators fromwaste vehicles by manual work which is troublesome and takes much time,and makes it possible to recover a lot of gas generators at a goodefficiency and low cost. Further, according to the present invention, itis possible to take out gas generators in the form of a single body sothat it is easier to classify the gas generators by the difference inmetallic materials. As a result thereof, gas generators can be put intomelting furnaces by the difference in metallic materials to recovermetals by the difference in metallic materials effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural drawing showing a crushing means suitable foreffectuating the method of the present invention and an apparatusconnected thereto.

FIG. 2 is a cross sectional drawing showing a rapid melting furnace foruse in effectuating the method of the present invention.

FIG. 3 and FIG. 4 are a cross sectional drawing of an open type cruciblefurnace for use in effectuating the method of the present invention anda cross sectional drawing of an arc furnace to use in the invention. Inthe drawings, 1: waste vehicle, 2: loader, 3: feed conveyor, 4:shredder, 8: belt conveyor, and 9: worker.

EXAMPLES

The present invention will now be described below with reference toexamples. FIG. 1 is a structural drawing showing a crushing meanssuitable for effectuating the method of the present invention and anapparatus connected thereto. Scrapped vehicles 1 from which useful partssuch as batteries and tires are detached are piled up. The vehicles inwhich air bag apparatuses are not installed may be contained in thesewaste vehicles. These waste vehicles can be pressed in advance. Thewaste vehicles 1 are put on a feed conveyor 3 by means of a loader 2 andsent to a crushing means, that is, a shredder 4. The waste vehicles 1are charged into the body of the shredder from a charging port 5 of theshredder and crushed therein. Light matters such as plastics out of thecrushed pieces are blown up from an exhaust port 6 at the upper side ofthe shredder and sent to, for example, a cyclone which is notillustrated and the light matters are recovered as dusts therein. Heavymatters are discharged from a discharging port 7 at the lower side andcarried to the outside on a belt conveyor 8. Gas generators of singlebodies separated from air bag apparatus, which have been detached fromthe waste vehicles by shredder 4, are contained in the crushed pieces onthe belt conveyor 8. Workers 9 recover the gas generators of singlebodies along the belt conveyor 8.

Example 1

Waste vehicles having air bag apparatuses mounted therein, which hadbeen pressed in advance, were charged into a shredder (2000 HP)manufactured by Tissenhenschel Co., Ltd. (Germany) by means of a feedconveyor at a rate of 2 vehicles per minute. The pieces of the crushedwaste vehicles were classified into light pieces and heavy pieces by anair current given by blowing air into the shredder. Among these pieces,the heavy pieces were discharged from the lower portion of the shredder.The weight of discharged heavy pieces accounted for about 90% of theweight of the charged waste vehicles. Gas generators installed in airbag apparatuses mounted in the waste vehicles were contained in the formof a single body in the discharged heavy pieces.

Before charging the gas generators taken out into a melting furnace, thenon-actuated gas generators can be actuated in advance by methods suchas heating.

Example 2

Ten non-actuated electric type gas generators were fixed at spaces of150 mm by metal meshes at upper and lower parts thereof. Then, the fixedgas generators were charged into an electric furnace maintained at 250°C. at a moving rate of 150 mm/minute. The first gas generation tookplace in about 5 minutes after starting charging, and the gas generationwas repeated at an interval of about one minute. The last gas generatorwas discharged from the electric furnace about 20 minutes later, and allgas generators were cooled down in the air outside the furnace for aboutone hour. All gas generators had been actuated.

Various melting furnaces can be used for a melting furnace into whichthe gas generators taken out are charged. FIG. 2 shows a rapid meltingfurnace. This furnace is a continuous melting furnace comprising a towertype melting furnace 11 having a high speed burner 10 (blowing speed:100 to 300 m/sec) built therein and a sealed type temperature rising andretaining furnace 12 combined therewith. The inside of the tower typemelting furnace 11 is sufficiently heated by exhaust heat of the highspeed burner 10 and a temperature rising burner 13, and therefore metalcharged from a charging port 14 will be rapidly molten.

Example 3

Gas generators were charged into the rapid melting furnace describedabove. Ten non-actuated gas generators having housings made of aluminumwere charged from the charging port 14 mixing with 500 kg of a usedaluminum material. The gas generators and the used aluminum materialwere heated in the tower type melting furnace 11 which has beensufficiently heated, and sound caused by the gas generators actuatedabout 30 seconds later since charging was recognized, and sounds causedby the gas generators actuated in succession were recognized up to 90seconds since then. The furnace was not damaged by the actuations of thegas generators. Aluminum was molten out of the gas generators andrecovered in the form of ingot. Metals (for example, stainless steelmetal mesh constituting a coolant) other than aluminum were not moltenand recovered separately from molten aluminum.

FIG. 3 shows another example of a melting furnace into which the gasgenerators are charged. This furnace is an open type crucible furnacehaving a structure in which a burner 16 is operated at the outside of acrucible 15 to heat molten metal in the inside thereof. A graphitecrucible or an iron-made crucible having a good heat conductivity isused as the crucible, and a high anti-heat insulating refractory 17 isused in the circumference of the crucible.

Example 4

One hundred actuated gas generators having housings made of aluminumwere charged into an iron made-crucible furnace (inner diameter: 760 mm,thickness: 35 mm and depth: 800 mm) having a capacity of 600 kgmanufactured by Okuyama Heavy Oil Furnace Co., Ltd. Aluminum was moltenout of the gas generators and accumulated at the bottom of the furnace.Metals (mainly stainless steel) other than aluminum remained in unmoltenstate at the upper side of molten metal. An unmolten metallic material18 was taken out by a dipper having holes, and the remaining moltenaluminum was scooped out by another dipper and poured into an iron-madeingot mold. Then, it was cooled down and recovered as aluminum metal.

FIG. 4 shows still another example of a melting furnace into which thegas generators are charged. This furnace is an arc type furnace which isone kind of an electric type furnaces, and the constitution thereofcomprises a hearth 19 for storing molten metal and a lid 20 for thermalinsulation/heat holding and supporting electrodes. The electrodes 21 aremovable upward and downward.

Example 5

Fifty non-actuated gas generators each having housing made of stainlesssteel were mixed with a used stainless steel material of 2500 kg andcharged into an arc type furnace having a capacity of 50 tons. Thecharged gas generators and the used stainless steel material were heatedto high temperatures at the upper part of the furnace, and the actuationof the gas generators as well as burning of oil and fat component(s)adhered on the used stainless steel material was confirmed. The gasgenerators were molten together with the used stainless steel materialand taken out of the hearth in the form of molten metal.

What is claimed is:
 1. A method for recovering metallic materials of gasgenerators for air bags from waste vehicles comprising:a) crushing wastevehicles in which air bag apparatuses are installed by a crushing meansadjusted so that crushed pieces have approximately the same size as thatof said gas generators, wherein the gas generators that are notsubstantially crushed can be separated from the air bag apparatuses, b)taking the gas generators out of the crushed pieces of the wastevehicles, c) charging the gas generators thus taken out into a meltingfurnace, and d) recovering the metallic materials of the gas generatorfrom the melting furnace.
 2. The method as claimed in claim 1, in whichthe crushing means is a crusher which crushes the waste vehicles byrotating blades.
 3. The method as claimed in claim 1, wherein some ofsaid gas generators have housings made of aluminum and some of said gasgenerators have housings made of stainless steel and wherein said methodfurther comprises the steps of taking out the gas generators byclassifying gas generators having housings made of aluminum from gasgenerators having housings made of stainless steel, separating said gasgenerators having housings made of aluminum from said gas generatorshaving housings made of stainless steel and charging the gas generatorshaving said aluminum housings into a melting furnace(s) separately fromgas generators having stainless steel housings.
 4. The method as claimedin claim 1, which comprises a step of actuating the gas generatorsbefore charging into the melting furnace.
 5. The method as claimed inclaim 4, in which the gas generators are actuated by heating.
 6. Themethod according to claim 1, wherein said melting furnace is a towermelting furnace, an open type crucible furnace, or an arc furnace.